// 动态吸附线条效果
!function(){
    // 获取或设置属性值的通用函数
    function o(w, v, i) { return w.getAttribute(v) || i }

    // 根据标签名获取元素集合
    function j(i) { return document.getElementsByTagName(i) }

    // 获取配置信息
    function l() {
        var i = j("script"),
            w = i.length,
            v = i[w - 1];
        return {
            l: w,
            z: o(v, "zIndex", -1),
            o: o(v, "opacity", 0.5),
            c: o(v, "color", "156,193,182"),
            n: o(v, "count", 99)
        }
    }

    // 设置画布大小
    function k() {
        r = u.width = window.innerWidth || document.documentElement.clientWidth || document.body.clientWidth,
        n = u.height = window.innerHeight || document.documentElement.clientHeight || document.body.clientHeight
    }

    // 清除画布并绘制粒子
    function b() {
        e.clearRect(0, 0, r, n);
        var w = [f].concat(t);
        var x, v, A, B, z, y;
        t.forEach(function(i) {
            i.x += i.xa,
            i.y += i.ya,
            i.xa *= i.x > r || i.x < 0 ? -1 : 1,
            i.ya *= i.y > n || i.y < 0 ? -1 : 1,
            e.fillRect(i.x - 0.5, i.y - 0.5, 1, 1);
            for (v = 0; v < w.length; v++) {
                x = w[v];
                if (i !== x && null !== x.x && null !== x.y) {
                    B = i.x - x.x,
                    z = i.y - x.y,
                    y = B * B + z * z;
                    if (y < x.max) {
                        if (x === f && y >= x.max / 2) {
                            i.x -= 0.03 * B,
                            i.y -= 0.03 * z;
                        }
                        A = (x.max - y) / x.max,
                        e.beginPath(),
                        e.lineWidth = A / 2,
                        e.strokeStyle = "rgba(" + s.c + "," + (A + 0.2) + ")",
                        e.moveTo(i.x, i.y),
                        e.lineTo(x.x, x.y),
                        e.stroke();
                    }
                }
            }
            w.splice(w.indexOf(i), 1);
        });
        m(b);
    }
    
    // 创建画布并初始化
    var u = document.createElement("canvas"),
        s = l(),
        c = "c_n" + s.l,
        e = u.getContext("2d"),
        r, n,
        m = window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame || function(i) { window.setTimeout(i, 1000 / 45) },
        a = Math.random,
        f = { x: null, y: null, max: 20000 };

    u.id = c;
    u.style.cssText = "position:fixed;top:0;left:0;z-index:" + s.z + ";opacity:" + s.o;
    j("body")[0].appendChild(u);
    k();
    window.onresize = k;
    
    // 鼠标点击事件
    window.onmousedown = function(i) {
        i = i || window.event;
        f.clicked = true;
    };
    
    // 鼠标移动事件
    window.onmousemove = function(i) { 
        i = i || window.event;
        if (f.clicked) {
            f.x = i.clientX, 
            f.y = i.clientY 
        }
    };

    // 鼠标释放事件
    window.onmouseup = function() {
        f.clicked = false;
        f.x = null;
        f.y = null;
    };

    // 鼠标抬起事件
    window.onmouseout = function() { 
        f.x = null, 
        f.y = null 
    };

    for (var t = [], p = 0; s.n > p; p++) {
        var h = a() * r;
        var g = a() * n;
        var q = 2 * a() - 1;
        var d = 2 * a() - 1;
        t.push({
            x: h, 
            y: g, 
            xa: q, 
            ya: d, 
            max: 6000
        });
    }

    setTimeout(function() { b() }, 100)
}();
